The vagus nerve: a true information highway

BRADLEY J. FIKES - Staff Writer

The vagus nerve is the longest nerve in the body, and one of the
most important. It sends commands to, and takes information from,
numerous important organs. People actually have two vagus nerves,
one for each side, running a roughly parallel course from brain to
bowels.

Originating in a part of the brain stem called the medulla
oblongata, the vagus nerve passes through the face, down the
throat, past the voice box, esophagus, lungs, heart, diaphragm and
intestines. Along the way, this great river of nervous impulses
throws off tributaries to these organs.

Vagus means "wandering" in medieval Latin, and now you know why.
Other cognates of the word are "vagrant," "vague" and
"vagabond."

Because it connects to so many organs, problems with the vagus
can take many forms. If the left or right vagus nerve is completely
cut near the top, the organs it controls are left partly
functioning. The vocal cords on the affected side don't work;
neither does the gag reflex on that side.

The multipurpose vagus nerve also controls sweating and
heartbeat. It acts as an inhibitor. Stimulating the nerve causes
the heart to slow down and also reduces activity of the diaphragm,
the sheet of muscle below the stomach used in breathing. These are
characteristic functions of the parasympathetic nervous system, to
which the vagus belongs. It balances the activity of the
sympathetic nervous system, which accelerates organ activities.

Overstimulation of the diaphragm plays a role in hiccups. As youmight expect, stimulating the vagus nerve can calm the diaphragm,ending this exasperating condition. A few years back, a doctorreported success stopping hiccups with an unorthodox method ofstimulating the vagus nerve -- a gloved finger inserted into therectum. In 2006, Francis Fesmire of the University of TennesseeCollege of Medicine received the dubious honor called the Ig Nobel
Prize for his medical paper: "Termination of intractable hiccupswith digital rectal massage."

In a more dignified approach to the problem, a medical device
called the vagus nerve stimulator has been used to control
intractable hiccups. The device sends electrical impulses into the
nerve. The vagus nerve stimulator has also been approved for the
treatment of uncontrolled epileptic seizures. It's implanted in the
chest near the collarbone, and turned on with a magnet when a
seizure is starting. The device is also being tested for treating
long-term intractable depression.

Other treatments involving the vagus nerve are in the testing
stages. One, to control obesity, takes advantage of the nerve's
connection to the stomach. The vagus nerve stimulates the stomach
to produce its acidic digestive juice, and causes the brain to
produce appetite-increasing hormones.

A study by researchers at UC San Francisco and the University of
Rochester has found that of 11 patients who have had the vagus
nerve connection to the stomach severed, 10 are losing weight one
year after the operation.